Casio CZ/ VZ/ FZ - Pro Series

Yea, check the VZ service manual. It's most likely that it's the same mechanism. 

My VZ-1 had the same symptoms, I opened it up, lifted off the rubber bubble pad and 
carefully blew out the dust. Don't wipe away the grease! That stuff is difficult to 
replace. If you clean that off you'll drastically reduce the reliability and life of the 
keyboard.

Also, be extra careful that you put all the wiring back in exactly the same positions. If 
you don't, you risk having the contacts slightly raised and loosing aftertouch 
sensitivity. There are a lot of screws and cabling to get through to access the 
keyboard contacts.